Corn spot basis bids at US Midwest river elevators eased on Thursday, but gained for soyabeans around the interior of the region, grain merchandisers said. Soft corn basis bids reflected limited demand for product shipment by barge to the US Gulf Coast. Barge bids for soyabeans held steady, underpinned by brisk demand and a lack of farmer sales. Corn and soyabean basis bids for elevators and processors around the Midwest were largely unchanged.